Electro Magnetics - Poynting Theorem Part 1

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Electro Magnetics - Poynting Theorem Part 1
Lecture By: Mr. Hari Om Singh, Tutorials Point India Private Limited

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Electro Magnetics Theory Course:
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TutorialsPoint_

my EM knowledge is so rusty from undergrad and my MS class is killing me. You're doing an amazing job helping me not to throw myself from the bridges around here LOL thanks bud!

tadehmirzakhanian

@10:25 I think there will be by 2 there

selvakumar-ikvg

Let take two identical positive charges q1 and q2. There are four points (a), (b), (c), (d) . q1 was initially located at point (a), and q2 was at point (d). Distance between (a) to (d) is taken 1 lightsecond. Distance between (b) and (c) is also about 1 lightsecond ( a little less)

q1is moved from (a) to (b) toward q2, and in a similar way, q2 is moved from (d) to (c) toward q1. Let say they both were pushed for half a second.
(For Energy given) Force on q1=Kq1q2/r^2
(For energy output) Force on q2 =Kq1q2/r'^2

When we think about r, we found that it would be somewhere between distance of (a) - (d) and (b) - (d), as the electric field of q2 will be the same there for 1 second. But for r′, it is between (a)-(d) and (b) - (c), so r>r′. Therefore, the force on q2 is greater.

Assume that you are q1 and are pushed for 1/2 second over a very short distance. You will find that field of q2 were the same there for that time period as a result of the velocity of the electric field. So, the q2 for q1 was at (d) during push. Thus, q1's average distance from q2 was somewhere between (a) - (d) and (b) - (d).

However, for r′ taken for force on q2 for receiving signal was different from r. Here, I am q2 and was moved at the same time, but when your changed electric field reached me after 1 second, I was also moved closer. So, for me, you moved closer, and I also moved a little closer to you, which makes my average distance from q1 less than r.
Seems like output energy(signal) was more than input given on q1.
Tell me how the velocity still not violating the law of conservation of energy

AnujKumar-sxws